1. Field of the Invention
The present invention relates to a composition for forming an electrically conductive layer and a process for forming a pattern using said composition. More specifically, the present invention relates to such a composition for pattern formation used for preventing charge-up occurring in electron beam lithography or focusing ion beam lithography, and a process for the formation of a resist pattern by use of said composition. The present invention relates also to such a composition for preventing charge-up occurring in an ion-implantation step and an ion-implantation process by use of said composition.
2. Description of the Related Art
In order to form an electron circuit element having a fine pattern, e.g., a semiconductor device or the like, a thin film formation technique and photolithographic etching technique have often been used. That is, a thin film layer such as an electrically conductive layer and insulating layer are formed on a substrate to be processed, by a method such as a puttering method and chemical vapor deposition method, following which a resist (photosensitive resin) is coated on the thin film layer by a method such as spin coating, and subsequently exposed to light, whereupon a pattern is formed by utilization of the phenomenon that a difference is caused in developing characteristics between the exposed part and unexposed part, e.g., that there is caused a difference therebetween in solubility to the developing solution, or the like. Wet etching or dry etching is conducted by use of this resist pattern as a mask, whereby a fine conductor pattern or insulating pattern is formed on a substrate to be processed.
As the light source in the exposure of a resist, there are used ultraviolet rays, X-rays, an electron beam, focusing ion beam and the like. Among them, according to electron beam lithography, a pattern can be directly drawn on a resist by scanning an electron beam, and therefore, the electron beam lithography has been widely used for the formation of a photomask or prototype logical circuit, for the production of a modicum-multikind type LSI such as an ASIC, which has recently presented increasing demand, and so forth. In addition, a focusing ion beam, also capable of effecting direct drawing, is scarcely scattered in a resist and therefore, exhibits a satisfactory rectilinear propagation property and excellent definition, and applications of focusing beam to specific devices requiring fine processing have been examined.
However, since a resist for an electron beam or focusing ion beam is an insulating material, when exposing it by use of an electron beam or ion beam, accumulation of an electric charge occurs, i.e., a charge-up phenomenon, which causes misregistration of a resist pattern. This misregistration becomes relatively higher as the pattern becomes finer, and has become a serious problem with the recently advanced integration of circuits. In addition, in the ion implantation step in the production of semiconductors, the ion-implantation is conducted through an insulating film such as an oxide film or resist, and a charge-up phenomenon occurs owing to the ion. Since a charge-up phenomenon causes an unevenness of ion distribution, lowering of ion-implantation controllability, and further dielectric breakdown of the substrate, this phenomenon is disadvantageous in that it adversely effects the properties of the device, thus lowering the reliability thereof.
Some techniques concerning charge-up prevention have already been reported. For example, attempts have been made to coat, on a pattern formation resist, aluminium (Japanese Unexamined Patent Publication (Kokai) No. 63-226926), ammonium polystyrenesulfonate (Japanese Unexamined Patent Publication (Kokai) No. 64-37015) or the like, in order to prevent the charge-up. The method of coating aluminum has the disadvantage that the steps become complicated. On the other hand, the process using ammonium polystyrenesulfonate has the defect that the charge-up-preventing effect is not satisfactory, though its steps are simple.
In addition, a report has been made that a composition containing a polymer of thienyl alkane sulfonic acid compound is useful as an antistatic agent (Japanese Unexamined Patent Publication (Kokai) No. 2-247219). However, this composition exhibits a strong acidity, for it contains a non-oxidative proton, and when a pattern is formed by use of the composition, an adverse effect is exerted upon the resist, element, wiring material or the like. Further, this composition causes practical disadvantages in that the production of a monomer becomes difficult, that disposal of waste liquid becomes complicated when producing semiconductors, and the like. In addition, a report has been made that an aqueous solution of a sulfonated polyaniline compound may be used as an antistatic agent (Japanese Unexamined Patent Publication (Kokai) No. 4-32848). However, this technical idea has the disadvantage that, since the structure of the polymer, the base to be blended, the solvent to be used and the like are not optimum, the conductivity is insufficient and charge-up cannot sufficiently be prevented.
On the other hand, the present inventors have proposed a process using a TCNQ complex as a conductive component (Japanese Unexamined Patent Publication (Kokai) No. 3-87743). Although this process is simple and its effects are satisfactory, since a ketone type or ether type organic solvent is used as a solvent, when a resist soluble in any of these solvents is used, it happens that the used solvent forms a mixed layer with the resist, the properties thereof being deteriorated. In addition, as the charge-up prevention method which has now been actually practiced in an ion-implantation step, there have been practiced a method of lowering the charge density, that of applying an electron shower onto a wafer, and the like. However, no definitive effect can be obtained by any of these methods.